Method of fractionating vapors



June'l3, 1933.

J. s. WALL .[S

METHOD OF FRACTIONATING VAPORS Filed March 30, 1931' I N VEN TOR. JO/Ifl3. MM

r- {1g 2. ATTO EY.

Patented June 13, 1933 UNITED STATES, PATENT OFFICE JOHN S. WALLIS, O!NEW YORK; N. Y., ASBIGNOB '10 LL PRODUCTS, INCORPORATED, OF NEW YOBL N.'Y L CORPORATION Oi! DELAWAQE IETHOD OI IBAOTIONA'IING VAPORSApplication fled. amen so, 1981. semi R0. 52am.

This invention relates to'improvements in fractionat ng hydrocarbonvapors or vapors of a similar character, and refers more parthrough thetower.

ticularly to a method of stripping side streams removed from afractionating tower. This method has to do with the stripping of sidestreams by introducing steam thereto and returning the steam andstripped vapors to a point in the tower where flashing of theva'porsoccurs or slightly therebelow, to reduce the partial pressure ofthe hydrocarbons which are supplied-to the tower at this point.

The single gure is a diagrammatic view of a distillation apparatus inwhich the in-' vention may be practised. Although the drawing disclosesa tube still connected to a fractionating tower with ro er condensingeguipment, any type of istillation still is a aptable to practising theinvention.

Referring to the drawing -a furnace is diagrammatically shown at 1L Oilis intro duced 'througli a pipe 2 and is circulated through a heatinzone in the'furnace where it is brought to distillation temperature. It

is'discharged from the furnace through a pipe 3 and is introduced intothe fractionate lng tower 4 where it flashes into vapor and is subjectedto the condensing action of liquid Hydrocarbons which. are coursed in anopposed dir'ection-to the passage of the vapor Uncondensed fractionspass over from the top of the tower throughfoutlet line 5 throughthe-condenser coil 6positioned in a condenser box 7 thence to a waterseparator 8 and finally to a reflux tank 9. From the re-' flux tank theoverhead-stream is removed through a pipe 10'and a ortion of thisdistillate recirculated throng the pipe 11, pump 12, and line 13 to becharged back into the top of the tower where it servesas afractionating-medium flowing against the vapors which rise through theseparate fractionating sta es of the'tower.

The ractionating tower shown at 4 is preferably of the bubble type,pools of liquid being" maintained at di erent heights in the tower.' Thevapprs risingthrough the tower are caused to bu ble through the liquidpools. Side reams are taken 01! .of the tower through pipes 14 and 15and directed to the stripping towers 16 and 17 respectively.

Steam may be generated by introducing water or exhaust steam throughpipe 18 into a heating coil or super-heater pos tioned in the furnaceo'rstill setting 1. The steam discharged passing out through the line 19is directed through pipes not shown to the perforated coils 20positioned in the bottom of side stream directed to the tower 16. iswithdrawn from 1 the stripping tower through a pipe 23 passed through acooler coil 24 and finally withdrawn from the system through the pipe25. The stripped side stream from the tower 17 is withdrawn through aline 26, thence directed through a cooling coil 27 to be discharged fromthe systern througha pipe 28. The bottom removed fromv the tower 4 isdiverted from the system through the pipe 29 and is passed through acooling coil 30 after which it is directed through a line 31 to storageor to further pro cessing. The control of the drawofi from the strippingtowers and the main fractionating, towers is preferably either bymanually op-" erated valves or by liquid-level controlled valves. Thisregulation is notshown on the drawing, as it forms no part of theinvention and is well-known practice.

The stripping steam and light vapors evolved from the towers 16 and 17pass off through vapor lines 32 and 33 which unite in a common line 34.This line 34 diverges into two separate lines 34and 34% The former isconnected into the fractionating tower below the' flash point or belowthe point at which the heated oil is supplied to the tower by thetransfer line 3. The pipe 34' is connected into the tower directlyopposite the flash point or at the same height in the tower ittt whichthe transfer pipe is connected thereo. 4

By connecting the vapor lines carrying the stripping steam and .lig tvapors to the fractionating tower at the point of flash orslightly'therebelow, the stripping steam and light vapors are reused toreduce the partial pressure of the vapors at the point of flash. This 5gives a lower outlet still temperature than would otherwise be possible.

Although but two side streams are shown, the invention contemplates theuse of a tower having any number of side streams taken off at differentheights in the tower. By manifolding the vapors and steam from theexternal stripping section, a considerable volume of vapors and steamare accumulated for return to the tower. With thisproposed method thestripping steam and light vapors removed from the stripping sectionsassist in stripping the bot toms in the tower and at the same timereduce the partiall'n'essure at the flash point in the tower, giving alower temperature of vaporization which reduces the stillvoutlettemperature for the same vaporization.

Previous practice has been to vent the external stripping sections atpoints in the tower at the same side streams are removed; Such practiceis probably best illustrated by the patent to J. W. Lewis, No.1,680,421, dated August 14,

As suggested, the conventional type of tube still connected to amulti-side stream fractionating tower With external stripping sectionshas been shown. This apparatus may be altered or varied withoutdeparting from the spirit and'scope of the invention which broadlypertains to the utilization of the steam and light vapors as a means forreducing the partial pressure of the medium introduced to thefractionating tower. This JOHN s. WALLIS.

elevation from which the reduction in partial pressure is accomplishedby introducing the vapors and steam from the stripping sections to apoint at or below the flash point of the tower. I claim as my invention:

1. The method of fractionating hydrocarbon oils including the stepsofheatingahydrocarbon oil to a vaporizin temperature, introducing theoil so heated into a fractionating zone having a plurality of stagesofconden- I sation, removing a liquid condensate from one stage ofcondensatign, stripping the condensate so removed in an externalstripping zone with steam, returning the vapors from the stripplng zoneto the fractionating zone and introducing them at a point at or belowthe point of introduction of the heated hydrocarbon oil, the methodbeing such as to reduce the partial pressure prevailing in thefractionatmg zone,

2. The method of fractionating hydro-. carbon oils including the stepsof heating a hydrocarbon oil to a distillation temperature while passingthe same in an elongated confined stream,

6 ed into a fractionating zone having a pluintroducing the oil so heat-

